The present invention relates to a low pressure mercury vapor discharge lamp including a discharge tube having a base surrounding an electrode sealing portion at the both ends of the discharge tube.
Hitherto, it is known that when a low pressure mercury vapor discharge lamp, for example, a fluorescent lamp, reaches the end of the lifetime, a temperature of an electrode sealing portion of the end of the discharge tube extremely increases. In order to prevent the temperature from extremely increasing at the end of the lifetime and to secure the safety at the end of the lifetime, it has been proposed that a thermal fuse provided in the vicinity of the end of the discharge tube is fused by heat at the end of the discharge tube, thereby interrupting a lighting circuit.
In the above-mentioned fluorescent lamp, rare gas and mercury are filled in the discharge tube. The both ends of the discharge tube are provided with an electrode sealing portion for holding an electrode. The electrode sealing portion is surrounded by a base. Inside the base and in the vicinity of the electrode sealing portion, a temperature protecting element is provided. The temperature protecting element is sensitive to the temperature rise of the electrode sealing portion at the end of the lifetime so as to produce a state in which electric current is interrupted.
The temperature protecting element is connected to at least one lead wire outside the electrode in series. The lead wire outside the electrode is connected to the temperature protecting element by caulking connection with the use of caulking components, or connected by soldering, and the like, after connection as a stranded wire.
In order to prevent the connecting part from short circuiting the other lead wire outside the electrode, the connecting part has a structure in which the caulking connection part is shielded with an insulating member, or a structure in which the caulking connection part is fixed to the inside of the base with a silicon resin member or adhesives.
Furthermore, the lead wire outside the electrode and the base lead terminal are connected to each other at the tip of the base lead terminal of the outside of the base by a soldering process, a melting process or a caulking process.
However, with the above-mentioned conventional fluorescent lamp, the operation efficiency in the process of connecting the lead wire outside the electrode and the temperature protecting element is bad and the process requires many steps and the high material cost. Therefore, the productivity is extremely bad.
Furthermore, in the above-mentioned fluorescent lamp, the connection between the lead wire outside the electrode and the temperature protecting element is performed inside the base, while the connection between the lead wire outside the electrode and the base lead terminal is performed outside the base. Consequently, the operation efficiency becomes worse, thus deteriorating the productivity.
It is an object of the present invention to provide a low pressure mercury vapor discharge lamp capable of radically improving the productivity by improving the operation efficiency and reducing the number of steps and the material cost.
In order to achieve the above-mentioned object, a low pressure mercury vapor discharge lamp of the present invention includes a discharge tube filled with rare gas and mercury, a base provided at the both ends of the discharge tube and surrounding an electrode sealing portion and a caulking terminal planted in the base and having a tip inside the base, wherein the base includes electric wiring and at least one of the electric wiring is connected to the caulking terminal to provide an electric connection inside the base. According to the above-mentioned low pressure mercury vapor discharge lamp, since the caulking terminal is planted and integrated into the base and the position of the caulking terminal is fixed, the caulking connection process can be automated. Furthermore, after the caulking connection, adhesives for attaching the caulking terminal to the inside of the base are not required, thus improving the operation efficiency and the productivity by reducing the number of steps and the material cost.
It is preferable that the above-mentioned low pressure vapor discharge lamp further includes a temperature protecting element in the base, wherein the temperature protecting element is caulking-connected to at least one lead wire outside the electrode by the caulking terminal.
Furthermore, it is preferable that the caulking terminal has one end projecting outside the base and another end projecting inside the base and includes at least one base lead terminal provided at the base that performs the caulking connection at the another end. According to the above-mentioned low pressure vapor discharge lamp, all the connecting operations can be performed only inside the base. Consequently, the number of the operation steps further can be reduced, and thus the operation efficiency can be improved.
Furthermore, it is preferable that a slit is provided at the tip of the caulking terminal and the caulking connection is performed by inserting the electric wiring into the slit.
Furthermore, it is preferable that the number of the caulking connection terminals is more than one and the direction in which the slit of each connection terminal is cut out is the same. According to the above-mentioned low pressure mercury vapor discharge lamp, since the directions of the slits for caulking connection are the same, the operation efficiency for setting lead wires in the caulking connecting process can be enhanced. Furthermore, since it is possible to fix the direction of caulking by the caulking equipment, the operation efficiency of the caulking process can be improved and the quality of the caulking connection can be stabilized.
Furthermore, it is preferable that the number of the base lead terminals is more than one and the position of the tip inside the base is almost the same in the height direction. According to the above-mentioned low pressure mercury vapor discharge lamp, since the height of the caulking connecting part can be fixed as constant, the operation efficiency of the caulking connection process further can be improved and the quality of the caulking connection can be stabilized.
Furthermore, it is preferable that a discrimination mark is formed on the base lead terminal and outside the base. According to the above-mentioned low pressure vapor discharge lamp, when the base lead terminal is planted in the base, the direction of the slits can be discriminated and controlled even from the outside of the base by using the discrimination mark. Therefore, the control of the direction of the slits can be controlled securely, thus stabilizing the quality of the caulking connection.
Furthermore, it is preferable that the discrimination mark has a convex shape or a concave shape.